Electron discharge tube



Aprifi 27, 1943., e. P. CHEVIGNY I 2,317,442

ELECTRON DISCHARGE TUBE Filed April 2, 1941 2 Sheets-Sheet l FIGJLINVENTOR.

GEORGES R CHEV/G/VY A TTORNEY;

April 1943- G. P. CHEVIGNY 2,317,44Z

ELECTRON DI SCHARGE TUBE Filed April 2, 1941 2 Sheets-Sheet 2 FIG. 3..

IN VEN TOR. GEORGES P. C/ffV/G/W Patented Apr. 27, 1943 UNITED STATESPATENT OFFICE ELECTRON DISCHARGE TUBE Application April 2, 1941, SerialNo. 386,514

In France March 30, 1940 6 Claims.

The present invention relates to electron discharge tubes and moreparticularly to power electron discharge tubes.

In tubes of this kind which are especially suitable as emission tubesintended for operating at high frequency, it is desirable to reduce to aminimum the capacities between the electrodes and the electrodeconnections and, for this purpose, to reduce to a minimum the lengths ofthese very connections and also the surfaces of the electrodesthemselves. It is furthermore desirable to provide a screening of thetube elements with respect to the sources of feed when these tubes areintended to operate at very high frequencies.

The object of the present invention is consequently the providing oftube structures and designs of electrodes and electrode connections thathave the above mentioned desirable features.

A power tube, according to one variation of the invention, may comprisea cathode, a control grid, and anode and auxiliary grids of which one atleast takes the part of a screen, one end of the insulating protectingenvelope of the tube being hermetically sealed by a conducting platethat serves as an electrical connection and as a mechanical support forthe anode. Cooling means are associated with the anode located withinthe insulating envelope of the tube, and the other end of the tube hassecured to it hermetically another metallic plate that serves as outputconnection for the screen grid; this plate is provided with insulatinghermetical ducts for the other tube electrodes. This last mentionedmetallic plate may be connected direct to a conducting screen outsidethe tube without any interposed insulating material.

According to another characteristic feature of the invention, the anodeis supported within the envelope by means of a cooling liquidcirculation jacket which surrounds it and to which it is securedhermetically, this jacket being supported by the above-mentioned endconducting plate.

These features, as well as others, are explained in detail hereunder inthe following description with reference to the appended drawings, inwhich:

Fig. 1 illustrates one example of an embodiment of a screen grid powertube that displays features of the invention;

Fig. 2 is a sectional view of a plane taken substantially along the line2--2 of the tube of Fig. 1, the screens being omitted for greaterclearness;

and

Fig. 3 shows detail of the filament structure of the tube of Fig. 1which gives a better view of the connection of the filament strips.

Referring to the drawings, and more particularly to Fig. 1, the tubestructure selected for illustrating the invention is a power tetrode.Within an insulating protecting envelope I it comprises a cylindricalshaped anode 2 closed at one end, as shown at 3; a screen grid thatconsists of a winding (not shown) is supported by rods indicated at 4; acontrol grid that likewise consists of a winding (not shown) is carriedby rods shown at 5 and a thermionic cathode that consists of twofilament strands in series 6 and 6'.

The two ends of the insulating protecting envelope l have connected tothem two metallic plates I- and 8, e. g. of copper and these plates arehermetically sealed to the protecting envelope I by means of flaringsleeves 9 and III, respectively, made of a metal such as copper. Thesesleeves 9 and ID are respectively brazed at one end on rims II and I2 ofthe metallic plates I and 8, the tightness of the joint of each platewith its sleeve being furthermore reinforced by peripheral solderings I3and I4, e. g. with tin. The other ends of the sleeves 9 and I0 aresealed to the ends of the insulating envelope I in any known manner, asshown at l5 and I6. It is to be observed that the metallic plate I onthe anode side is connected to sleeve 8 by means of rim II whichsurrounds sleeve 9, while the metallic plate 8 at the other end isconnected to sleeve III by rim l2 which cooperates with a peripheral rimII of sleeve III which is of such a shape that it has an annular surfaceI8 that cooperates with the corresponding surface of plate 8 so as toform between these two surfaces a. narrow annular compartment [9 whichis connected to the inside of the tube in order to insure pumpingbetween the plates. This extension of the annular plate 8 around thisend of the tube provides a screening effect which may be increased bymeans of another annular metallic plate (not shown) that is connecteddirect to rim [1, all in such a way that the screen constituted in thisway displays practically no electrical discontinuity.

The screen grid is electrically and mechanically connected to themetallic plate 8 by means of rigid rods 20, four in the example shown inthe drawings (Fig. 2). These rods are bent as shown at 2| in order tofollow the line of the fictitious cylinder of the screen grid alongwhich they extend, as already described. They are held in position atthis point by a rigid metallic ring 22 on which they are secured, e. g.by means of soldered beads 23. Connecting wires 24 connect this ring 22to a conducting annular member 25 in which the rods are secured, themechanical centering of the screen grid assembly being assured by thecentering of this annular member on the metallic plate 8, i. e. by thecentering oi screws 25 that secure the annular member 25 to the metallicplate 8.

In this way, electrical continuity is provided between screen grid 4 andthe metallic plate 8 within the tube and, assaid above, the connec tionof this metallic plate to a screen grid 4 t its outside part.

In the metallic plate 8 there are provided th leads required for thecontrol grid and cathode electrodes. If the tube were a pentode, thesuppressor grid would be directly connected to the cathode within thetube and this would save the use of extra leads.

The control grid connection lead comprises two.

coaxial metallic sleeves 21 and 28 which are connected at one end by aninsulating annular portion 29 that is sealed to the ends of the coaxialsleeve. The outer sleeve 21 is screwed direct into a correspondingsleeve portion 30 that is provided in the metallic plate 8. Thetightness of the joint is furthermore insured by means of tin soldering,for example, as shown at 3|. The inner sleeve 28 is brazed and solderedto a metallic rod 32 which may hold the rigid threaded end 33 of aflexible conductor 34 that serves as a terminal for supplying potentialsto the control grid. This conducting rod 32 is secured within the tubeto a supporting plate 35 which is hollowed at its center and to which itis are welded, for example, as shown at 36. This supporting ends ofstrip 6 are secured by beads 54 to the ends of rod 41 and arm 52 of thefork, while the ends of strip 6' are secured by beads 54' to the ends ofrod 41' and arm 52' of the fork respectively. These two strips offilament are consequently connected in series between the current leadsdescribed above.

The other ends of the looped strips 6 and 6' are passed through eyelets55 and 55' installed on two different metallic rings of an end insulator56 of a known type. The longitudinal play of strips 6 and 8' on passingthrough the eyelets 55 and 55' permits free longitudinal expanplate ismade integral, e. g. by brazing or by the threading of an annular member3'! in which the ends of the grid supporting rods 5 are secured. Theserods 5 are furthermore kept exactly centered by means of the ring 38 towhich they are secured, e. g. by means of soldered beads 39.

The two leads for supplying the heating current for the filament shapedcathode 55' each consists of a metallic sleeve 4040' screwed into acorresponding sleeve portion 4| of plate 8. The tightness of the jointis insured by soldering with tin, for example, as shown at 42. The outerend of each sleeve 40 and 40' is sealed to an insulating sleeve 43 whichhas its other end sealed to a metallic cap 44, e. g. of copper, in whichthere is the end of an attached current supply conducting rod 45 whichthus passes through the metallic plate 8 without being in contact withit. Two supporting plates 46 and 46' are respectively secured, e. g.screwed, to the ends of rods 45, and the other ends of these supportingplates 4648', respectively, admit the ends of two rods 4l-4l' for theelectrical connection and the mechanical support of the filament strips6 and 6'. These rods 41 and 41' are maintained in spaced relation at twopoints of their lengths by split stays 48 and 49 which are of such shapethat they lock not only rods 41 and 41' but also a rod 50 extendinggenerally axially oi the electrode structure. These different rods aresecured to the stays 48 and 49, e. g. by means of beads as shown at 5|.As can be seen more clearly in Fig. 3, this central rod 50 carries aguide fork with two arms 52 and 52', and it is secured to the rod by asoldered bead 53. Each of the filament strips 6 and 8' is of loop shapeand with parallel wires as shown in the drawings and the sion orcontraction of the strips of filament while insuring their lateralguidance. is secured to the end of the axial rod 50 in any suitablemanner. Besides, it is possible to adopt a difierent construction of theterminal device for the filaments, or even a different arrangement ofthe filaments within the design while retaining a discharge tubestructure'in accordance with the invention.

At the terminal end of the electrode structure on the side of the closedpart 3 of the anode there are likewise centering rings 51 and 58 for thesupporting rods 4 and 5 of the screen grid and control grid,respectively. Ring 51 of the screen grid may be provided with a terminalscreen plate 59 that closes this end of the filament-grid electrodestructure with respect to the anode.

With a construction according to the invention, e. g. the structureshown in the drawings in which the end metallic plate 8 actuallysupports the cathode-grid assembly, it is to be observed that when thecathode or one of the grids is damaged. it is easy to repair it orreplace it by unsoldering plate 8, removing this plate and the electrodeassembly supported by it and then, after the repairs are made, replacingthis unit that has been disassembled and pumping out the tube again.

Although anode 2 which surrounds the other electrode is disposed withinenvelope I in which the vacuum has been made, it must be cooled in theordinary way for power tubes. This cooling is effected within theenvelope itself, as shown in the drawings. For this purpose, a cylinder60 of a diameter greater than that of anode 2 is disposed around theanode and is hermetically connected to the open end of the same, e. g.by being screwed to the end of this anode as shown at SI, andfurthermore by welding as shown at 62 in order to insure tightness ofthe joint. The other end of cylinder 60 is screwed and soldered tosleeve 9 as shown at 63, and it rests against the metallic plate I. Bythis method of fitting, cylinder forms part of the cooling liquidcirculation jacket of anode 2 while providing a mechanical support forthe anode in the general construction of the tube.

Between cylinder 60 and anode 2 there is inserted another cylinder 84which forms a deflector for the cooling liquid circulation system. Thisdeflecting cylinder 64 is constricted at its base at,.65 and is solderedas shown at 68 to a central sleeve portion 81 of the metallic plate 1.This sleeve portion is open in such a way as to form a passage for thecooling liquid of the anode. The metallic plate I is perforated atanother spot 68 between cylinder 60 and the end 65 of cylinder 64 inorder to provide another passage for the cooling liquid.

The anode is electrically connected to the metallic plate I by means ofbraided wires, as shown at 69, which pass within the constricted portionInsulator 58 of sleeve 64 and are soldered within the sleeve portion 61of plate I.

On this plate I and to the outside of the tube, bolts as shown at securea hollowed block H for the supply and removal of the cooling liquid.This block II comprises a liquid supply channel 12 that leads to sleeve61 of plate I, and a liquid circulation compartment I3 that is providedwith an outlet passage for the liquid (not shown). With an arrangementof this kind, a cooling liquid under pressure may be made to flow alongthe surface of the anode 2 and to cool this anode to the desiredtemperature. It is to be observed that the joint between sleeve 9 andthe protecting envelope is cooled at the same time.

Cylindrical screens 14 for the open anode end and 15 for the feedconnections assembly of the other electrodes are likewise provided inthe structure.

It is evident that the anode design shown in the drawings may bemodified without departing from the scope of the invention. For example,the anode may be of the conventional tubular anode type that forms partof the wall and has its two ends connected to insulating portions of theenvelope that carry metallic end sealings which serve as outputconnections for two electrodes passing through insulating portions ofthese metallic sealings.

Furthermore, the invention is not limited to tetrode tubes as describedby way of example, but is on the contrary capable of being usedadvantageously with tubes of any desired number of electrodes, whethersimple or multiple. a triode tube it may likewise be suitable to providea screen like that formed by plate 8 in the tube shown in the drawings;this screen may be extended as desired without electrical discontinuityoutside the tube, the cathode and control grid connections issuing, forexample, through this screen which will not be connected to an electrodeof the tube.

What is claimed is:

1. An electron discharge device comprising an envelope and an electrodesystem including two electrodes within said envelope, one of saidelectrodes having a portion insulatingly sealed to said envelope at oneend of said device, and means accurately securing the other of saidelectrodes in said envelope in a particular relation with respect tosaid one electrode, said securing means including a flange-shapedportion on said envelope at the end opposite said one end of saiddevice, a plate-like member cooperatingly fitting on said flange-shapedportion, said other electrode being rigidly mounted on said platelikemember. and means sealing said plate-like member to said flange-shapedportion.

2. An electron discharge device according to For claim 1, wherein saidflange-shaped portion includes a flat portion extending generallytransversely of the axis of the device and an annular portion extendinggenerally axially thereof, said plate-like member being fitted uponsaidflat portion and extending in close adjacency to the inner wall ofsaid annular portion.

3. An electrondischarge device according to claim 1, wherein saidflange-shaped portion includes a fiat portion extending generallytransversely of the axis of the device and an annular portion extendinggenerally axially thereof, said plate-like member being fitted upon saidflat portion and extending in close adjacency to the inner wall of saidannular portion, and wherein said sealing means is solder bridgingadjacent portions of the inner wall of said annular portion and saidplate-like member.

4. An electron discharge device comprising an envelope and an electrodesystem including cathode, grid, and anode means within said envelope,said anode means having a portion insulatingly sealed through saidenvelope at one end of said device, and means accurately securing saidcathode and grid means in said envelope in a particular relation withrespect to-said anode means, said securing means including aflangeshaped portion on said envelope at the end opposite said one endof said device, a plate-like member cooperatingly fitting on saidflangeshaped portion, said grid and cathode means being rigidly mountedon said plate-like member,

flange-shaped portion.

5. An electron discharge device comprising anenvelope and an electrodesystem including two electrodes within said envelope, one of saidelectrodes having a portion insulatlngly sealed to said envelope, andmeans accurately securing the other of said electrodes in a particularrelation with respect to said one electrode, said securing meansincluding a conductive flange-shaped portion forming part of saidenvelope and axially aligned with said electrode system, a conductiveplate-like member cooperatingly fitting said flange-shaped portion, saidother electrode being rigidly mounted on said plate-like member, andmeans sealing said plate-like member to said flange-shaped portion.

6. An electron discharge device according to claim 5, wherein said otherelectrode has lead-in means and said plate-like member is conductive andalso carries a generally tubular and axially aligned shielding memberextending within the device substantially co-extensive with the lead-inmeans for said other electrode, whereby said tubular member, saidplate-like member, and said flange-shaped portion cooperate to form anextended shield for said lead-in means.

GEORGES PAUL CHEVIGNY.

